1. Field of the Invention
The present invention relates to an optical pickup for reproduction, recording, or purge of optical disks or magnetic disks (hereinafter, referred to simply as “disk(s)”) such as DVD/RW.
2. Description of the Related Art
Describing now a principle of an optical pickup, as shown in FIG. 7, information recorded in a disk D is read by projecting a laser light O1 from a laser diode LD attached via a holder 2 to the outer periphery of abase 1 through a diffraction grating G, a half mirror HM, a collimator lens QWP, and an objective lens OL and receiving the reflected light by a photodiode PD via the half mirror HM.
In the above-described structure, there may be a case in which the laser light O1 is displaced from an optical axis O2 of the collimator lens QWP due to variations in angle of diffusion of the laser light O1, and a technology for correcting the displacement is disclosed in JP-A-2-220228. According to this technology, as shown in FIG. 8 and FIG. 9, a laser hole 2a for fitting the laser diode LD therein is formed through the center of a rectangular holder 2, which is long in a direction X—X and short in a direction Y—Y. Then, insertion holes 2b for inserting adjusting screws are formed at four corners of the holder 2, the holder 2 is provided with a projection 2A projecting concentrically with the laser hole 2a on the back surface of the holder 2, four adjusting screws 3 are inserted into the respective insertion holes 2b, and coil springs 4 are fitted on the respective adjusting screws 3.
Describing now to a mounting procedure of the laser diode LD, the laser diode LD is fixed to the holder 2 with machine screws 5, and the projection 2A is fitted to an opening 1a of the base 1. Then, the respective adjusting screws 3 are screwed into the screw holes 1b of the base 1 in a state in which the respective coil springs 4 are interposed between the base 1 and the holder 2 to engage the laser diode LD with the outer periphery of the base 1 via the holder 2, and the laser light O1 is positioned on the optical axis O2 of the collimator lens QWP. Subsequently, by finely adjusting the screwing amount of the respective adjusting screws 3 against a resilient force of the respective coil springs 4, the posture of the holder 2 is slightly rotated in the directions indicated by arrows a and b about a contact point P between the opening 1a and the projection 2A for adjustment, and displacement of the center of the strength of the parallel ray due to variations in angle of diffusion of the laser light O1 is corrected, so that the laserlight O1 is aligned with the optical axis O2 of the collimator lens QWP.
In the structure in the related art, the projection 2A on the holder 2 is adapted to be fitted into the opening 1a. Therefore, when the laser light O1 is displaced from the optical axis O2 of the collimator lens QWP along the outer periphery of the base 1 vertically and laterally X—X, Y—Y, such displacement cannot be corrected. Consequently, there is no other way than discarding the holder 2, which results in increased cost. Since it is also adapted to perform fine adjustment of the screwing amount of the respective adjusting screws 3 to correct the posture of the holder 2 and hence there are many adjusting screws 3, fine adjustment of these screws is a troublesome work since it takes time and a lot of trouble. In addition, since a plurality of adjusting screws 3 and the coil springs 4 are required, which increases the number of parts, the manufacturing cost increases as well.